If you have been using Infraworks 2014, you might have noticed that there is an issue with some of the trees. Notably, the road style Boulevard with Trees and another particular tree. The result shows the trunk of the trees as transparent. See image below…

1. In Windows explorer, find your Infraworks resource folder. The path is usually something like this:

C:\ProgramData\Autodesk\InfraWorks 2014\Resources

Note that ProgramData is a system folder that is often hidden by default, so that you might not see ProgramData in c:.

2. Inside the resource folder, the texture file that causes the problem in your case is in this subfolder:

<Your_ResourceFolder>\assets\3DSMaxContent\Trees\PalmTree007_Var01

Here, there should be a file called PalmBark001_Diffuse.jpg

Henrik-B also states the problem is that the models contain some monochrome .jpg textures that are not handled correctly by Infraworks 2014. The attached file is another version of the same image, but converted to color-rgb. I obtained it by opening the jpg in IrfanView, choosing "Increase Color Depth" in the image menu, and overwriting the texture file with the converted one.